/Engine/Source/Runtime/GeometryCore/Public/MeshAdapter.h
Second version of the above faster adapter  for the case where triangle indices are packed into an integer vector type instead of flat
template<typename IndexVectorType, typename OutRealType, typename InVectorType> struct TIndexVectorMeshArrayAdapter
constTArray< I...
SourceTriangles
constTArray< I...
SourceVertices